This invention relates to refrigeration systems for cooling multiple chambers, and more particularly to apparatus and method for chamber temperature control by on/off control of refrigerant flow through individual evaporator coils in the chambers.
Commercial refrigeration systems are used for cooling multiple chambers such as in supermarkets wherein individual chambers must be kept at various temperatures from xe2x88x9240 degrees to about 50 degrees F. for proper food storage. These systems generally employ many compressors in parallel. The compressed refrigerant is condensed to a liquid in a condenser. The liquid refrigerant is then fed to individual evaporator coils in the various chambers, where the liquid refrigerant evaporates to the gaseous state with absorption of heat. A blower blows air through the cooling coil and the cooled air then cools the chamber. The refrigerant gas then returns through the return gas line to the compressors. Control of the amount of cooling by each individual coil is generally by means of an evaporator pressure regulator (EPR) in each return gas line that meters the flow rate of gas. It adjusts the flow of gas to maintain a suction pressure selected across the valve to maintain a selected temperature for the chamber. The system is arranged to start and stop selected compressors to maintain a particular gas pressure at the input to the compressor bank to idle unneeded compressors for economy of operation. Some EPRs are equipped with an on/off solenoid valve to stop the flow of refrigerant during defrosting. Applicant has found that these systems of the prior art lack efficiency of operation and fail to regulate temperature accurately.
It is an accordingly an object of the invention to provide refrigeration systems that control cooling more accurately and more efficiently than conventional systems. It is another object that the system not rely upon EPRs for control of cooling. It is yet another object that control of refrigerant flow be by on/off valve in each gas refrigerant line leaving each coil. It is yet another object of the invention to provide a method of modifying a conventional refrigerator system that has EPRs with on/off valves by adjusting the EPRs to wide open and operating the on/off valve with a controller that turns the on/off valve on or off on the basis of the temperature sensed at the coil. These and other objects, features, and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings in which like elements are designated by like reference characters in the various drawing figures.